1. Field
The invention relates to methods and apparatus for entry of characters on a computer keyboard, and specifically relates to methods and apparatus for selecting among a plurality of various cases, or functions, controlled by individual keys.
2. State of the Art
Typical manual typewriters have a multiplicity of type bars, each of which is mechanically linked to a key. Keys and type bars are made to do double duty by forming two characters on each type bar. A "shift" key repositions the entire array of type bars to determine whether the first or the second character on the type bars is to be imprinted on the paper. The array of type bars is repositioned into the normal position by a spring when the shift key is released. Typing an upper-case key therefore requires that the shift key first be depressed, then second that the desired letter key be struck while the shift key is still depressed. A separate "shift lock" key often is used to lock the type bars in shifted position, and maintain them in that condition until released by a separate act of the user.
Many features of today's standard computer keyboards are traceable to the characteristics of such manual typewriters. Among these features is the QWERTY layout ("QWERTY" being the letters generated by the six upper left alphabetic keys) and the requirement that a "shift" key be pressed and held while a character key is struck to generate an upper case character. The "shift" key therefore selects between two cases or functions of the character key, where each case or function generates a unique character code when activated.
Many keyboards also have one or more "control" "function" or "alt" keys that change the function or character of keys struck while the said "control" "function" or "alt" key is held in a manner similar to the operation of the "shift" key. The "control", "function", "alt", and "shift" keys are all key-modifier keys, while the key having a function that is altered by the key-modifier key may be referred to as the modifiable key.
Generally, the key-modifier keys of a standard QWERTY-layout keyboard are located at the sides of a keyboard where they are struck with the little finger. There are many people with limited hand mobility who find that operating these keys with the little finger is awkward. Additionally, the placement of key-modifier keys on many keyboards is such that simultaneous operation of key-modifier keys and modifiable keys is difficult for those who have limited hand mobility, who type with one hand, or who type with a mouthstick.
Northgate sells a keyboard having an operating mode in which key-modifier keys alter the function of the first modifiable key struck following activation of the key-modifier key. The key-modifier function is then automatically cleared such that the function of the second following modifiable key is not altered by the key-modifier key. This is a "sticky" key-modifier key. The Northgate keyboard has the key-modifier keys located in the conventional locations, and has an operating mode in which the key-modifier keys behave conventionally.
Many users of keyboards have been trained to "touch type". Such users typically begin typing by placing the four fingers of the left hand over the A, S, D, and F keys, with the thumb over the spacebar, and the four fingers of the right hand over the J, K, L, and; keys, with the thumb over the spacebar, known as the "home position". The alphabetic keys are operated by moving the finger in the nearest column to the appropriate key arrangement of the letter keys, and requires learned motions to strike them such that such persons type by feel without looking at the keyboard while they type.
Touch-typists at their maximum speed require not only the arrangement of letter keys on a keyboard to match the standard keyboard for which they are trained, whether that standard be the QWERTY or DVORAK layouts, but that the size and spacing of the keys also be standard. Touch-typists find that the nonstandard, tiny keys of many pocket organizers and pocket computers are very difficult to use.
Touch-typing becomes substantially more difficult if the key pitch, or the center to center spacing of keys on the keyboard is less than 16 millimeters in the horizontal direction. Some studies, such as that cited in the March, 1993 Computer Shopper on page 346, in the sidebar entitled "Keyboard Size: How Small is Too Small", show that the smallest desirable key pitch for easy acceptance by touch-typists is approximately seventeen and eight-tenths millimeter center-to-center horizontally. Desktop computers generally have an eighteen to nineteen millimeter key pitch between horizontally adjacent keys, as specified in ANSI standard HFS 100-1988, with nineteen millimeters being the most common. The key pitch specified by the standard is eighteen to twenty-one millimeters in the vertical direction.
The standard keyboard layout also provides a single space bar reachable with either thumb. Touch-typists are often trained to hit the spacebar with only one thumb, the remaining thumb being unused while typing.
There are keyboards on the market that have separate spacebars intended for use by each thumb separately. These keyboards include the "ergonomic" keyboards that have the keyboard array split between the "G" and "H" keys, with the halves rotated to permit keeping the wrists straight while typing. While these "ergonomic" keyboards have separate spacebars for each thumb, these spacebars generate the same encoded character, a space.
Some touch-typists will accept keyboards with nonstandard size, spacing, and location for key modifier, function, special character, and numeric keys more readily than they will accept nonstandard alphabetic key locations. Such typists will accept these because there are many different standards for the locations and sizes of key modifier, function, and special character keys, and because these keys tend to be among those used less often.
Modern keyboards use an electronic device to scan the array of keys to detect when a key is struck and for generating a key code specific to the key struck. This electronic device may, but need not, be located on the same circuit board as the array of keys. This electronic device may comprise dedicated electronic circuitry or may comprise a small microprocessor programmed to scan the array. The microprocessor translates the key code into a standard key code format and communicate the translated key code to the computer, often serially. Alternatively, the processor of an organizer or portable computer can be programmed to scan the keys.
Many electronic devices for scanning the array of keys operate by driving a first voltage on a row line common to a plurality of key switches. There is more than one row line, the remaining row lines resistively connected to a second voltage, as is a plurality of column lines. Each key switch in a row connects to a different column line. When a key switch is activated, and the associated row line is driven to the first voltage, the first voltage being coupled onto, and which may be sensed on the associated column line. Each key is therefore defined by the intersection of a row and a column. The keyboard is scanned by driving the first voltage on each of the row lines sequentially, while monitoring the column lines. This technique permits the keyboard scanning device to correctly identify at least two simultaneously active keys, possibly more depending upon their location in the key array.
Electronically scanned keyboards also may have a diode in series with each key switch. Diodes allow the scanning device to correctly identify all active, or struck, keys even if several keys are struck simultaneously. Keys, such as the "shift", "control" and "alt" keys, that are intended to be struck simultaneously with other keys, may have such diodes and be located in their own row or column so as to ensure that they are correctly recognized despite whichever other keys are struck.